Glossary

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Slimliar to drive shaft but more usually associated with launching an impact moling or similar tool.

Launch Seal

A mechanical seal, usually composed of a rubber flange that is mounted to the wall of the drive shaft. The flange seal is distended by the MTBM as it passes through, creating a seal to prevent water or lubrication inflow into the shaft during tunneling operations.

Lead Pipe

The leading pipe manufactured to fit the rear of the jacking shield and over which the trailing end of the shield is fitted.

Leading Interjack Pipe

The pipe immediately ahead of, or attached to, the interjack shield.

Live Insertion

Method of installation of a liner while the product pipe remains in service.

Localised Repair

Repair work on a pipe, particularly sewerage, for lengths less than the run between two adjacent access points.

Location

Trenchless procedures for identifying the site of underground utilities, infrastructure, obstructions, etc. without excavation or with minimum excavation.

Locator

An electronic instrument used to determine the position and strength of electro-magnetic signals emitted from a transmitter sonde in the pilot head of a boring system, or an impact mole tool or from existing underground services which have been energised. Sometimes referred to as a Walkover System.

Low Load Method

A pipe jacking method in which separate provision is made to carry the jacking load, the pipe being installed carrying little or none of the jacking force.

Lubrication

Means of reducing friction either around a pipe being jacked or a shaft being sunk into the ground.